Experimental studies on the lead accumulation in the cestode Moniezia expansa (Cestoda: Anoplocephalidae) and its final host (Ovis aries)

Significance of Intestinal Helminth Infection and Animal Sex for Mercury Concentrations in Two Rodent Species

We compared the effects of animal gender, species, and intestinal helminth burden on mercury concentrations in rodents. Total mercury concentrations were determined in the liver and kidney tissues of 80 small rodents (44 yellow-necked mice, Apodemus flavicollis, and 36 bank voles, Myodes glareolus) captured in the Ore Mountains (northwest Bohemia, Czech Republic). Overall, 25/80 (32%) of animals were infected by intestinal helminths. The differences in mercury concentration between rodents infected and not infected with intestinal helminths were not statistically significant. Statistically significant differences in mercury concentrations were found only between voles and mice (that were not infected with intestinal helminths). This suggests the differences may be associated with host genetics. Apodemus flavicollis body tissues had significantly lower (P=0.01) mean Hg concentrations (0.032 mg/kg) than Myodes glareolus (0.279 mg/kg), provided that animals were not infected by intestinal helminths; if the animals were infected by intestinal helminths, the difference between both groups was insignificant. The effect of gender in this study was significant only for voles (without helminth infection); for mice (either with or without helminth infection) the differences between genders were not significant. Myodes glareolus males had significantly lower (P=0.03) Hg concentrations in liver and kidney tissues (0.050 mg/kg) than Myodes glareolus females (0.122 mg/kg). These results reveal the importance of considering species and gender when evaluating mercury concentrations.

How tapeworm infection and consumption of a Cd and Zn hyperaccumulating plant may affect Cu, Fe, and Mn concentrations in an animal-a plant consumer and tapeworm host

This study evaluated the effects of a hyperaccumulator plant (Arabidopsis halleri), containing surplus of cadmium (Cd) and zinc (Zn) and being an admixture to the rat feed, on concentrations of copper (Cu), iron (Fe), and manganese (Mn) in the tissues of experimental rats infected/uninfected with the tapeworm (Hymenolepis diminuta). Male Wistar rats were divided into three groups (00, P0, and PT); the P0 and PT animals were fed a standard mixture for rats (ST-1) supplemented with the plant A. halleri at a weekly Zn and Cd dosage of 123 and 1 mg, respectively. Moreover, rats from the group PT were infected with the tapeworm. The group 00 served as control animals fed only ST-1 having no tapeworm infection. Rats were euthanized after 6 weeks, and Cu, Fe, and Mn levels were determined in rat and tapeworm tissues. The results indicated that both the consumption of hyperaccumulator plant and/or presence of tapeworms did have significant effect on Cu, Fe, and Mn concentrations in the host tissues. Concentrations of all the elements were higher in the rat liver and partially kidneys than in the tapeworms, and the concentrations of Cu, Fe, and Mn were affected by the consumption of Cd/Zn hyperaccumulator plants. Particularly, Fe concentrations in all rat tissues were significantly increased by consumption of A. halleri while decreased by the presence of tapeworms. Overall, the consumption of a Cd/Zn hyperaccumulator plant and tapeworm infection cause an imbalance in Cu, Fe, and Mn concentrations in the tissues of a consumer (experimental rats).

Analysis of lead pollution levels within an urban ecosystem using the cestode Hymenolepis diminuta and its rat hosts as bioindicators

The overall goal of this study was to use the Rattus spp./Hymenolepis diminuta model to assess environmental lead pollution in different landscape units of an urban ecosystem. Rats of the genus Rattus were collected from three shanty towns and three residential neighbourhoods of the city of Buenos Aires. Concentrations of lead in the livers of wild rats and in their parasite H. diminuta were measured using inductively coupled plasma mass spectrometry (ICP-MS). The landscape unit and tissue type had a significant effect on lead concentration, being higher in residential neighbourhoods as well as in H. diminuta tissue. Nevertheless, no significant differences were found for the mean lead concentration in livers between uninfected and infected rats. Since the available information describing heavy-metal pollution within the city of Buenos Aires is scarce, the results of this study allow us to update data about the extent of biologically available lead contamination. Considering that rats and H. diminuta are distributed worldwide, this monitoring system for lead pollution might be applied successfully in other urban ecosystems.

Parasite responses to pollution: what we know and where we go in 'Environmental Parasitology'

Environmental parasitology deals with the interactions between parasites and pollutants in the environment. Their sensitivity to pollutants and environmental disturbances makes many parasite taxa useful indicators of environmental health and anthropogenic impact. Over the last 20 years, three main research directions have been shown to be highly promising and relevant, namely parasites as accumulation indicators for selected pollutants, parasites as effect indicators, and the role of parasites interacting with established bioindicators. The current paper focuses on the potential use of parasites as indicators of environmental pollution and the interactions with their hosts. By reviewing some of the most recent findings in the field of environmental parasitology, we summarize the current state of the art and try to identify promising ideas for future research directions. In detail, we address the suitability of parasites as accumulation indicators and their possible application to demonstrate biological availability of pollutants; the role of parasites as pollutant sinks; the interaction between parasites and biomarkers focusing on combined effects of parasitism and pollution on the health of their hosts; and the use of parasites as indicators of contaminants and ecosystem health. Therefore, this review highlights the application of parasites as indicators at different biological scales, from the organismal to the ecosystem.

Is the tapeworm able to affect tissue Pb-concentrations in white rat?

The effect of gastrointestinal helminths on Pb accumulation in the host body is ambiguous. A laboratory experiment with Rattus norvegicus/Hymenolepis diminuta model was conducted to determine Pb toxicokinetics in a terrestrial host-parasite system. The ET-AAS or ICP-OES techniques were used to determine Pb concentrations (CPb) in both tapeworms and host tissues (kidney, liver, bone, testes, muscle and intestinal wall). Concerning the entire host-parasite system, the highest CPb were detected in H. diminuta. Rat kidneys and bone were the only two tissues whose mean Pb levels were lower in parasitized animals than they were in non-infected subjects after both levels of exposure. At low Pb exposure, parasitization slightly changed the Pb toxicokinetics in the host body. However, with respect to tissue at the same exposure level, no significant differences were detected between the parasitized and non-parasitized animals and no significant correlations were found between CPb in tapeworms and those of host tissues. The results of this study indicate that H. diminuta does not protect rat from elevated Pb exposure even if tapeworm accumulates a higher portion of ingested Pb dose compared with that of the most Pb-loaded host soft tissue. The portion of Pb dose accumulated in H. diminuta correlates positively with parasite biomass.

Effect of Acanthocephalus lucii infection on total mercury concentrations in muscle and gonads of fish host (Perca fluviatilis)

The samples from 13 perches (Perca fluviatilis) - muscle with skin and bones; fish gonads; and acanthocephalan parasites were analysed for mercury (Hg). Hg concentrations were present in all analysed samples. There were found no statistically significant difference in Hg concentration in fish tissues between perches either with or without infection by the acanthocephalan parasite, Acanthocephalus lucii). In this study there was no evidence that acanthocephalan worms accumulate mercury from hosts. For this reason, A. lucii is not a suitable bioindicator for mercury pollution.

Effect of lead in water on the absorption of copper, iron, manganese and zinc by sheep (Ovis aries) infected with sheep tapeworm (Moniezia expansa)

The sheep tapeworm (Moniezia expansa) and its host Ovis aries were analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES) for their copper, iron, manganese, zinc and lead levels. Element concentrations in cestode parasites were compared to those in various organs (liver, kidney, and muscle) of sheep. Tapeworms in the small intestine of sheep that were administered 2g of Pb(CH(3)COO)(2) per os daily (7 days) had significantly higher lead concentrations than sheep tissues. Cu levels significantly increased after Pb administration in sheep muscle and sheep tapeworms. Contrarily, Zn content significantly decreased in sheep muscle, but significantly increased in sheep tapeworms. However, Mn content significantly decreased after Pb administration in sheep tapeworms. Furthermore, Fe content significantly decreased after Pb administration in sheep liver and kidneys.

Intestinal parasite Acanthocephalus lucii (Acanthocephala) from European perch (Perca fluviatilis) as a bioindicator for lead pollution in the stream "Jevanský potok" near Prague, Czech Republic

Lead concentrations in the tissues of perch and its parasites were determined as mg/kg dw. Lead was found at higher concentrations in the acanthocephalans (11.56) than in different tissues (liver, gonads and muscle with skin and bone) of perch. With respect to fish tissues, the highest concentrations of lead were present in the liver (1.24), followed by the gonads (0.57) whereas the lowest concentrations were in the muscle with skin and bone (0.21). The bioconcentration factors for lead indicated that parasites accumulate metals to a higher degree than fish tissues--lead concentrations in acanthocephalans were 9.32, 19.27 and 55.05 higher than in liver, gonads and muscles of host, respectively.